When you make an ILS CAT3 (a/b/c) approach, which chart are you taking? I mean, I just know CAT1 and 2........

Question

.... charts, where the limits (visibility, DA/DH) are written. But if you look at the CAT2 chart, there is written that the DH is minimum 100 ft, so you couldn't take this one, because a CAT3 approach has not a DH...

Answer 1

Good answer geoff, I'll see if I can elaborate a bit...

You have specific category 3 plates for the ils. Additionally, category 3 approaches are broken down further to cat IIIa, with a dh of less than 100ft, or no dh and a rvr of no less that 655 ft.

Cat IIIb can have either no dh, or a dh of less than 50 ft, and no less than 165 ft rvr.

Cat IIIc has no dh and no rvr, but the aircraft must be able to land itself. The airplane must be equipped, and you must be trained in category 3 approaches. (I.e., unless you're part 121, you ain't flying this one)

http://avn.faa.gov/d-tpp/0804/00320I9RC3...

Answer 2

I'm not entirely clear on what you are asking here, but I'll take a stab at a response.

If you're talking about a specific approach then you have to be sure that a Cat III approach even exists.  You certainly can't use the Cat II approach, but a Cat IIIa and IIIb approach can both have a DH, only the Cat IIIc specifically doesn't have a DH.

I hope it helps.  It might help to restate your question if I'm way out to lunch on what you're asking.